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How do we know DNA is the genetic material?

How do we know DNA is the genetic material?. Griffith and later Avery 2 strains of pneumonia causing bacteria: rough and smooth TRANSFORMATION. How do we know DNA is the genetic material?. Hershey and Chase Bacteria and bacteriophages (viruses) Radioactive sulfur and phosphorus.

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How do we know DNA is the genetic material?

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  1. How do we know DNA is the genetic material? • Griffith and later Avery • 2 strains of pneumonia causing bacteria: rough and smooth • TRANSFORMATION

  2. How do we know DNA is the genetic material? • Hershey and Chase • Bacteria and bacteriophages (viruses) • Radioactive sulfur and phosphorus

  3. How do we know the structure of DNA? • Chargaff’s rules – BASE-PAIRING RULES

  4. How do we know the structure of DNA? • Franklin • X-ray shows shape is two twisted strands

  5. How do we know the structure of DNA? • Watson and Crick • Build model of DOUBLE HELIX • Where are the bases? • Where are the sugars? • Where are the phosphates?

  6. Structure of DNA • Polymer of nucleotides (monomer) • Nucleotide – sugar + phosphate + base • Sugar – deoxyribose • Bases – purines – 2 rings – adenine and guanine pyrimidines – 1 ring – cytosine and thymine • Base-pairing rules – purine to pyrimidine! A bonds to T G bonds to C

  7. Structure of DNA • Double helix • Double – 2 strands • Helix – a spiral • Looks somewhat like a twisted ladder • Sides of ladder – sugar and phosphate • Steps of ladder – nitrogenous bases • Nucleotides are held to each other by covalent bonds • Bases are held together by hydrogen bonds

  8. DNA REPLICATION • Precedes cell division: mitosis, meiosis, binary fission • Occurs during interphase • Replication – DNA copies DNA • CAN YOU SEQUENCE THE STEPS? • CAN YOU WRITE THE STEPS? • EACH NEW DNA MOLECULE CONSISTS OF ONE OLD STRAND AND ONE NEW STRAND

  9. PROTEIN SYNTHESIS • How does cell use DNA code to build protein? • 2 processes: TRANSCRIPTION and TRANSLATION

  10. PROTEIN SYNTHESIS • Requires the help of many enzymes and RNA • RNA • Single stranded • Sugar : ribose • Nitrogenous bases: adenine, guanine, cytosine, URACIL • What are the base pairing rules? • 3 types involved in protein synthesis • Messenger RNA – mRNA • Ribosomal RNA – rRNA • Transfer RNA - tRNA

  11. TRANSCRIPTION • Occurs in nucleus of eukaryotes– Where does it occur in prokaryotes? • DNA is copied by messenger RNA • How does mRNA know where to begin copying? • Can you sequence the steps? • Can you write the steps?

  12. TRANSLATION • Occurs in cytoplasm at the ribosome • messenger RNA is read (decoded) by the ribosome; transfer RNA supplies the amino acids to build the protein (polypeptide) • How does the ribosome know where the beginning and end of the message are? • Can you sequence the steps? • Can you write the steps? • Do you know the base pairing rules? • Can you use a codon chart to determine the order of the amino acids?

  13. MUTATION • What is a mutation? • What is the difference between a point mutation and a chromosome mutation? • Can you recognize and explain the effects of the following point mutations? • Substitution • Frame shift (due to additon or deletion of a base)

  14. MUTATION • Can you recognize and explain the effects of the following chromosome mutations? • Deletion • Inversion • Translocation • Duplication

  15. What is the significance of mutations? • Neutral • Disrupt cell function • Source of genetic variation – source of NEW genetic information • Exploited by human beings to improve or develop new plants and animals. • polyploidy

  16. Chromosome Structure • Can you distinguish between chromatin and chromosome? When is each seen in the cell? • What are histones and nucleosomes? • How are prokaryotic chromosomes different from eukaryotic chromosomes? • What are genes? Where are they located?

  17. Editing of mRNA • In eukaryotes the mRNA copy of DNA must be edited before it leaves the nucleus? • Why? • What is removed from the mRNA? Introns or Exons?

  18. What do genes code for? What do these molecules do in cells?

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